This invention relates to a method and apparatus for using the alkali metal recovered from alkali metal-containing scrap. The invention further relates to making master alloy using the lithium recovered from aluminum-lithium alloy scrap.
Fuel costs continue to be economically significant in today's aerospace industry. Aircraft designers and manufacturers are constantly striving to improve overall efficiency and performance. Such improvements may be accomplished by reducing the effective weight of materials used to manufacture component parts while maintaining the strength, toughness, corrosion resistance and/or other properties desired for such component parts. In recent years, aluminum-lithium alloys have been receiving more attention as candidates for structural metal applications in the aerospace industry. It is well recognized that additions of lithium to aluminum often results in reduced alloy density and, thus, lower effective weight. Since many manufacturing, thermal treatment and machining techniques relating to aluminum-lithium alloys are still in their experimental or developmental stages, large quantities of aluminum-lithium alloy scrap are being generated for every pound of usable metal produced. For cost, processing and disposal concerns, it would be desirable to recycle most of the lithium within such scrap for subsequent metal alloy production. Although lithium-containing scrap is usually separated from other metal scrap for handling and/or remelting purposes, aluminum-lithium alloy scrap may still contain variable quantities of still undesirable elements, such as zinc, manganese, titanium and iron. The presence of these latter elements makes it difficult to merely recast alloy scrap directly into marketable ingots.
Because of increasing costs associated with mining lithium ores and refining substantially pure lithium therefrom, alternative methods continue to be sought for recovering lithium from lithium-containing scrap. Standard recovery techniques for other metals, including magnesium, are not always applicable to aluminum-lithium alloy scrap. Molten lithium is highly susceptible to oxidation and hydrogen contamination while causing most refractory materials in contact with it to rapidly deteriorate or otherwise corrode away.